I nearly finishing my research on the saddle tank hatches today. I apology to Dougie and Pat for misleading them about the differences in the shape of the hatches.
http://models.rokket.biz/index.php?topic=124.msg6627#msg6627 As it has turn out that were are two different shapes hatches. There are five hatches along the saddle tank (Fig. 1).
Fig. 1. Hatch 1 to 5 - Stern to bow.
I am almost certain there is only one vent valve and this is
Hatch 3 as illustrate in the plan below. Also there is no internal arms system to open this valve, you would need to be on the surface to open and closed it.
from uboatarchive.net
http://www.uboatarchive.net/U-570Plate16.htmHatchesHatch 1 access to Main ballast and reserve fuel oil tank 2
Hatch 2 access to reg. tanks and reserve fuel oil tank 1
Hatch 3 Vent valve for reg. tank 2
Hatch 4 access to Neg. buoyancy tank
Hatch 5 access to Main ballast and reserve fuel oil tank 4
By using the patches of the missing hatches on
U-995 and counting the frames and was able to place the hatches in there correct locations. Below is a list of the real distance between the end of the stern to the centre of the hatch. If your model is 1:72 scale just divide the number by 72.
DistanceHatch 1 27,750 mm
Hatch 2 30,250 mm
Hatch 3 33,750 mm
Hatch 4 35,275 mm
Hatch 5 37,350 mm
Size and shapeHatch 1 about 60% sure on the shape and orientation, but should be 550mm by 400mm in size. I have not clear pictures of this hatch.
Hatch 2 not 100% sure on the shape or orientation but likely 550mm by 400mm in size. I have not clear pictures of this hatch.
Hatch 3 400mm - Circle
Hatch 4 400mm by 550mm in size.
Hatch 5 400mm by 550mm in size.
As yet I have seen no different between any VIIC